>>Another idea, Oliver Sack researched aurea's during migraine attacks. So
>it is possible that with a head bang you temporarilly deprive your
>visual cortex of input after which this areas go and generate
>chaotic-like patterns.
I like that idea. But I think that the visual cortex is not going "offline"
from its inputs. Synaptic transmission between neurons (i.e. the first layers
of visual perception and the visual cortex) is normally very stable and not or
only little disturbed by mechanical stimuli from outside the brain. But it is
known that visual recognition (seeing pictures, extracting things that belong
together) needs corellated activity between different neuronal layers. The
timing therefore is very crucial. This could be the point the "hit on the
head" interacts with neuronal activity. If the timing, which is responsible
for recognition, is disturbed, the "impression" of seeing is gone and the area
generates chaotic-like patterns (they can no longer be decoded from the brain)
Well, this is speculation, but I think no one wants to start a labority test
(too little participants :-)).
Wolfgang
wstein at rhrk.uni-kl.de